This is a book about the ways in which various intellectuals in the post-classical Mediterranean imagined the human community as a unified, homogenous whole composed of a diversity of parts. More specifically, it explores how authors of the 2nd century CE adopted & adapted a particular ethnic & cultural discourse that had been elaborated by late 5th- & 4th-century BCE Athenian intellectuals. At the center of this book is a series of contests over the meaning of lineage & descent & the extent to which the political community is or ought to be coterminous with what we might call a biologically homogenous collectivity. The study suggests that early imperial intellectuals found in late classical & early Hellenistic thought a way of accommodating the claims of both ethnicity & culture in a single discourse of communal identity. The idea of the unity of humankind evolved in the 5th & 4th centuries as a response to & an engine for the creation of a rapidly shrinking & increasingly integrated oikoumen. The increased presence of outsiders in the classical city-state as well as the creation of sources of authority that lay outside of the polis destabilized the idea of the polis as a kin group (natio). Beginning in the early 4th century & gaining great momentum in the wake of Alexander's conquest of the East, traditional dichotomies such as Greek & barbarian lost much of their explanatory power. In the 2nd-century CE, by contrast, the Roman empire imposed a political space that was imagined by many to be coterminous with the oikoumen itself. One of the central claims of this study is that the forms of cosmopolitan & ecumenical thought that emerged in both moments did so as responses to the idea that the natio--the kin group--is (or ought to be) the basis for any human collectivity. Acknowledgments Introduction Nature, culture & the boundaries of the human community After ethnicity: Zeno as citizen The rhetoric of unity "A pure world of signs": language & empire The origins of human wisdom The unity of the divine Conclusion Bibliography Index